Akaryali, Enver

The mineralization area (Altinpinar, Torul-Gümüşhane) is situated in the Southern Zone of the Eastern Pontides Orogenic Belt (EPOB), which is one of the important metallogenic provinces in the Alpine-Himalayan belt and is intruded by the late Carboniferous granitic rocks (Gümüşhane Granitoid), an early to middle Jurassic volcano-sedimentary unit consisting mainly of basaltic-andesitic volcanic and pyroclastic rocks (Şenköy Formation) and Eocene basaltic-andesitic volcanic rocks (Alibaba Formation). The studied Pb-Zn ± Au mineralizations are related to silica veins ranging from a few millimeters to a maximum of 40. cm in thickness and are localized within fracture zones developed along the contact between the Gümüşhane Granitoid and Şenköy Formation. Silicic, sulfidic, hematitic, argillic, intense chloritic and carbonate alteration are the most common types from the fault lines toward the outer zones. Cavity filling and banded structures are widely observed. The mineral paragenesis comprises galena, sphalerite, pyrite, chalcopyrite, tennantite and quartz. Mineral chemistry studies indicate that ion exchange occurs between Zn and Fe in sphalerites, and the Zn/Cd ratio of sphalerites varies between 50.65 and 144.64. The homogenization temperatures measured from fluid inclusions vary between 170. °C and 380. °C, especially between 250. °C and 300. °C, and the wt.% NaCl eqv. salinity of ore-forming fluids is between 2.4 and 7.3 (4.7 on average), supporting an epithermal system in their origin. The values of sulfur isotopes, which are obtained from pyrite and galena minerals, range between - 8.3‰ and - 2.3‰, indicating that sulfur, which enables mineral formation, originates from magmatic genesis. The average formation temperature of the ore is 317. °C as determined with a sulfur isotope geothermometer. The values of oxygen and hydrogen isotopes vary between 8.5‰ and 10.2‰ and - 91‰ and -73‰, respectively. With regard to the compositions of oxygen and hydrogen isotopes, fluids comprising the mineralization are formed by the mixture of magmatic water and meteoric water. This situation is supported by the fact that the increase in the homogenization temperature indicates dilution with surface water but depends on the increase in the salinity of fluid inclusions. Considering all the data, it is clear that the studied mineralization is an epithermal vein-type mineralization that is related to granitic magmas.

AtıfScopus29·WoS24·OpenAlex32

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Eyuboglu, Yener; Santosh, M.; Yi, Keewook; Tuysuz, Necati; Korkmaz, Sadettin; Akaryali, Enver; Dudas, Francis O.; Bektas, Osman

The Meso-Cenozoic geodynamic evolution of the eastern Pontides orogenic belt provides a key to evaluate the volcanogenic massive sulfide (VMS) deposits associated with convergent margin tectonics in a Cordilleran-type orogenic belt. Here we present new geological, geochemical and zircon U-Pb geochronological data, and attempt to characterize the metallogeny through a comprehensive overview of the important VMS mineralizations in the belt. The VMS deposits in the northern part of the eastern Pontides orogenic belt occur in two different stratigraphic horizons consisting mainly of felsic volcanic rocks within the late Cretaceous sequence. SHRIMP zircon U-Pb analyses from ore-bearing dacites yield weighted mean Pb-206/U-238 ages ranging between 91.1 +/- 1.3 and 82.6 +/- 1 Ma. The felsic rocks of first and second horizons reveal geochemical characteristics of subduction-related calc-alkaline and shoshonitic magmas, respectively, in continental arcs and represent the immature and mature stages of a late Cretaceous magmatic arc. The nature of the late Cretaceous magmatism in the northern part of the eastern Pontides orogenic belt and the various lithological associations including volcaniclastics, mudstones and sedimentary facies indicate a rift-related environment where dacitic volcanism was predominant. The eastern Pontides VMS deposits are located within the caldera-like depressions and are closely associated with dome-like structures of felsic magmas, with their distribution controlled by fracture systems. Based on a detailed analyses of the geological, geophysical and geodynamic information, we propose that the VMS deposits were generated either in intra arc or near arc region of the eastern Pontides orogenic belt during the southward subduction of the Tethys oceanic lithosphere. (C) 2013 Elsevier B.V. All rights reserved.

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